Yamaha 90 no fire

[BRR]

The yamaha 90 I am working on will only fire if I disconnect the yellow wires coming out of the cdi? It's the only way it will run, what does this mean?

[25XS]

Well, first off, how about telling us the year, model, whether it's 2-stroke or 4-stroke, and could you verify the wires are "just yellow", and not a yellow/black combination?

You should be able to start here and test your way thru it: http://www.cdielectronics.com/troubleshootingguide/

The 1992 to 2009 3-cylinder 2-stroke begins on Page 155

[88workcar]

Have you disconnected the external harness, if not, do so. Then use the brown on the start solenoid. Pull it loose and just touch it to the hot side, and check fire

[BRR]

It's a 1998 yamaha 90 2 stroke. I will check spark with controls unhooked.

[BRR]

Still no fire with controls disconnected.

[25XS]

Instructions to troubleshoot "No Spark on any cylinder" were linked in my previous post... Reconnect your controls, then it says to disconnect the white wire from ignition box (this is the stop circuit wire and eliminates any grounding from emergency lanyard, wire harness, key switch, etc... Everything) Do that and recheck for spark. If still none, the next group of diagnostics require you to have at the very least a volt/ohm meter to check circuit resistance on several items, and a DVA (Direct Voltage Adapter) to "read & hold" pulses of DC voltage while cranking that you can not see with just a volt/ohm meter.
You need to click the link and just methodically follow the diagnostic guide.

Again... Yellow Wires? are not mentioned in the ignition diagnostics. Are you certain you have yellow wires (not white, oily orange, greasy tan, etc..?)

[BRR]

Finally found it. It was a bad ground wire.

[25XS]

I hope you got some help from the CDI Electronics Troubleshooting Guide link I posted...

Your fix was literally "Step 2. Inspect and clean all engine and ignition ground connections."